JPH01133072A - Color electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent splashing of a toner image from a photosensitive body to a recovering roller and to obtain the sharp and high-density color image by providing a mechanism which impresses the voltage of the same polarity as the polarity of the electrostatic charge polarity of the photosensitive body to the recovering roller and providing a mechanism which attaches and detaches the recovering roller from the photosensitive body to the title device. CONSTITUTION:This electrophotographic device is provided with a color image forming means which forms the color image on the photosensitive body 40 by repeating electrostatic charging, exposing and developing stages for each of plural colors, a transfer means 46 which transfers the color image on the photosensitive body 4 to paper, the recovering roller 41 which attracts and removes the magnetic carrier sticking to the photosensitive body 40 by a magnetic brush developing method, and a power supply 42 which impresses the voltage of the same polarity as the electrostatic charge polarity of the photosensitive body 40 to the recovering roller 41. The tendency of the toner image to splashing from the photosensitive body 40 to the recovering roller 41 is thereby prevented and the sharp color image is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color electrophotographic device that can be used in a hard copy device such as a color copying machine or printer.

Conventional technology Traditionally, charging, exposure, and development are repeated multiple times to form multiple toner images of different colors on an electrophotographic photoreceptor (hereinafter referred to as photoreceptor), and then the toner images are transferred all at once to paper. Various color electrophotographic apparatuses have been proposed for obtaining color images. (For example, Japanese Patent Application Laid-Open No. 60-95456) In Figs. 2 and 3, a conventional example of an apparatus using such a color electrophotographic apparatus is shown. 2 is a corona charger that uniformly positively charges the surface of the photoconductor 1; 3 is a laser beam scanner; 4, 5, 6, and 7 are yellow (Y) and magenta (
M), a developing device containing cyan (C) and black (Bk) developers separately, 8 is plain paper, 9 is a static elimination lamp for facilitating electrostatic transfer of the toner image onto the plain paper 8, 10 1 is a corona charger for electrostatically transferring the toner image onto plain paper; 11 is a heat fixing device; 12 is a device for removing toner remaining on the photoreceptor 1 after electrostatically transferring the toner image onto plain paper 8; A cleaning blade 13 is a static elimination lamp for bringing the charged potential of the photoreceptor to an initial state.

The configuration of the developing device 4.5.6.7 is shown in FIG.

14 is a two-component developer (hereinafter referred to as developer) consisting of a mixture of positively charged toner and magnetic carrier; 15 is an aluminum developing sleeve; 16 is a magnetic roller;
7 is a layer thickness regulation blade that regulates the layer thickness of the developer; 18 is a scraping plate; 19 is a rotary blade that stirs the developer 14;
20 is a toner for replenishment, 21 is a toner replenishment roller, 22
is a power supply that generates a voltage that is a combination of a positive DC voltage and a high-voltage AC voltage. To make the developing device ready for development, the developing sleeve 15 is connected to the power source 22.

To make development impossible, the developing sleeve 15 is electrically floated or grounded, or a negative DC voltage is applied to the developing sleeve 15.

Next, a method of forming a color image using the color electrophotographic apparatus described above will be described. First, corona charger 2
After positively charging the photoconductor 1, the laser beam scanner 3 scans and exposes a yellow image signal to form a negative electrostatic latent image (the image area is exposed and the electrostatic charge potential of the photoconductor is attenuated). latent image). Then, the electrostatic latent image is reversely developed into a negative/positive state using a developing device 4 containing Y toner, thereby forming a yellow toner image on the photoreceptor 1. At this time, only the developing device 4 containing the Y toner is set to a developing condition that causes the toner to fly away, but the other developing devices 5 to 7 are adjusted to a state that the toner does not fly off. After development with the Y toner, the entire surface of the photoconductor 1 is irradiated with a discharge lamp 13 to optically eliminate the yellow electrostatic latent image.

Next, the steps of charging, exposure, development, and photostatic discharge are repeated in the same manner as the method used to form the yellow toner image, to form Y, M, C, and Bk toner images on the photoreceptor 1. After the formation of all toner images is completed, the electrostatic latent images are optically neutralized in advance using a static eliminating lamp 9, and the toner images are electrostatically transferred onto plain paper 8 using a corona charger 2. The toner image transferred to the plain paper 8 is heated and fixed by a heating fixing device 11. On the other hand, the toner remaining on the photoreceptor 1 after electrostatic transfer is removed by the cleaning blade 12, completing one cycle of color image formation.

Problems to be Solved by the Invention When image formation is performed using the color electrophotographic apparatus described above, when the toner concentration of the developer decreases, carriers in the developer are electrostatically attracted to the photoreceptor. So-called "carrier adhesion" occurred. It has been found that when this carrier adhesion occurs, significant damage is caused to the photoreceptor during the process of transferring the toner image from the photoreceptor to paper and the process of cleaning the photoreceptor. As a method for removing the carriers attached to the photoreceptor, there is a method in which a magnetic collection roller is installed near the photoreceptor and the carriers are attracted to the collection roller or roller by magnetic force. In this method, the collection roller does not have an electrostatic function and is therefore usually electrically suspended or grounded.

However, when this collection roller is used in an electrophotographic device that obtains a color image by superimposing toner images on a photoreceptor, the toner formed on the photoreceptor may fly back from the photoreceptor to the collection roller. It was found that the color image on the photoreceptor was disturbed.

In view of this point, the present invention has been developed to collect toner images from the photoreceptor by collecting rollers installed for the purpose of removing carriers attached to the photoreceptor when toner images of multiple colors are combined on the photoreceptor to obtain a color image. An object of the present invention is to provide a color electrophotographic device which prevents back-flying and obtains clear color images.

Means for Solving the Problems The present invention provides a color image forming means for forming a color image on a photoconductor by repeating charging, exposure, and development steps for each of a plurality of colors; A transfer means for transferring an image onto paper, a collection roller for adsorbing and removing magnetic carriers attached to a photoreceptor by a magnetic brush development method, and a power source for applying a voltage having the same polarity as the charging polarity of the photoreceptor to the collection roller. This is a color electrophotographic device having the following functions.

Another invention provides a color image forming means for forming a color image on a photoreceptor by repeating charging, exposure, and development steps for each of a plurality of colors, and for transferring the color image on the photoreceptor onto paper. This color electrophotographic apparatus includes a transfer means, a collection roller that adsorbs and removes magnetic carriers attached to a photoreceptor using a magnetic brush development method, and a mechanism that moves the collection roller toward and away from the photoreceptor.

According to the above-described structure, the present invention prevents the toner image from flying back from the photoreceptor to the collection roller by applying a voltage having the same polarity as the charged polarity of the photoreceptor to the collection roller, thereby producing a clear color image. get.

Further, according to another aspect of the present invention, by moving the collection roller toward and away from the photoreceptor, the toner image is prevented from flying back to the collection roller from the photoreceptor, and a clear color image is obtained.

Embodiment The principle of the present invention will be explained using FIGS. 4 and 5.

In a color electrophotographic device that superimposes toner images of multiple colors on a photoreceptor and transfers them all at once to paper, the developed toner image is charged again by a corona charger as shown in Figure 4. Ru. At this time, the photoreceptor 24 to which the toner 23 has adhered
In this case, the photoreceptor under the toner is also charged. Therefore, at this time, the toner 23 is attached to the photoreceptor 24 charged to the same polarity. In this state, for example, if a grounded carrier collection roller 25 exists near the photoreceptor 24, toner will fly back from the charged photoreceptor 24 to the grounded collection roller 25. This back-flying occurs because a large electric field strength is generated between the photoreceptor 24 below the toner 23 and the collecting roller 25. Therefore, there are two possible methods for preventing this toner from flying back. 1
One is to reduce the potential difference, and the other is to increase the distance between the electrodes. A possible method for the former is to apply a voltage to the collection roller that is approximately the same potential as that of the photoreceptor to eliminate the potential difference between the photoreceptor and the collection roller. A possible measure is to move the photoreceptor away from the photoreceptor.

Hereinafter, specific embodiments of the present invention will be described in more detail with reference to FIG.

The developing devices 26, 27, and 28 are non-contact type non-magnetic one-component developing devices that use a DC electric field to scatter the toner, and the toner is triboelectrically charged with a conductive fur brush 29, 30, 31 that is in contact with the developing roller. Aluminum developing roller 32.3
3.34, a thin layer of toner is formed by blades 35, 36, 37. The developer 26 is yellow (Y), the developer 27 is magenta (M), the developer 2 is
8 contains cyan (C) insulating toner. The developing device 38 is a contact type developing device containing a two-component developer consisting of an insulating toner and a magnetic carrier, which is widely used in electrophotographic devices. and developing roller 32, 33, 34.
The developing devices were disposed facing each other around the photoreceptor 40 while keeping the developing gap between the photoreceptor 40 and the photoreceptor 40 constant. Each developing device is attached with a separation mechanism that brings it close to the photoreceptor during development and separates it when not developing.

The specifications and development conditions of the black developer 38 and the physical properties of the toner are shown below.

・Developer specifications and developing conditions Diameter of developing roller 39: 22 m Circumferential speed of developing roller 39: 320 mm/s developing roller 39
Thickness of the developer layer on the surface: 400 μm Direction of rotation of the developing roller 39: Opposite direction to the photoreceptor 40 (same traveling direction) Development gap (gap between the surface of the developing roller and the surface of the photoreceptor): 300 μm during development, when not developing 2 num [Developer physical properties] Type of developer: Two-component developer consisting of toner and carrier Average particle size of carrier: Approx. 50μI Type of carrier: Teflon coated ferrite Toner charge amount: +10μC/g Toner average particle size: 8μm Toner specific dielectricity Ratio: Approximately 2 The specifications and development conditions of the yellow, magenta, and cyan developing devices and physical properties of the toners are shown below.

・Developer specifications and development conditions Developing roller diameter: 20+I1m Developing roller circumferential speed: 160 m/s Developing roller rotation direction: Opposite direction to photoreceptor 40 (same traveling direction) Toner layer thickness on developing roller = 30 μm Development gap (
Gap between developing roller surface and photoreceptor surface): 150 μm during development, 2 ugliness when not developed [Toner physical properties] Toner charge amount: +3 μC/g Average particle size: 10 μm Relative dielectric constant: Approx. 2 41 is the collection of magnet It was a roller (diameter 20W1, made of soft iron, 8 magnetic poles, 800 Gauss), and was installed 1 mm apart from the photoreceptor 40. A high voltage power source 42 is connected to the recovery roller 41. The photoreceptor 40 is an amorphous 5e-Te photoreceptor drum 40 with a diameter of 152+am, sensitized to long wavelengths in the infrared region (photosensitive layer thickness: 60 μm, dielectric constant: 7, function-separated selenium sensitized to long wavelengths in the infrared region). A photoreceptor) was used and rotated at a circumferential speed of 160 m1/s. This photoreceptor 40 is connected to a charger 43 (scorotron charger, corona voltage: +7 kV,
It was charged to a charging potential of +900 . Next, a semiconductor laser 44 with a wavelength of 790 nm is
was caused to emit light, and a negative black signal was exposed on the photoreceptor 40 to form an electrostatic latent image. The latent image is transferred to the developing roller 39 by +60
A black toner image was formed by reversal development using a black developing device 38 in a developing state to which 0 V was applied.

Thereafter, the carrier attached to the photoreceptor 40 was adsorbed by the collection roller 41 . The photoreceptor 40 was neutralized by a static elimination lamp 45.

Next, the photoreceptor 40 was again charged to +600 cm using the corona charger 41 (Scorotron charger, corona voltage: +7 kV, grid voltage -600 cm).

At this time, the charged potential of the photoreceptor 40 to which the black toner was attached was 600V. Thereafter, the photoconductor 40 is exposed to signal light corresponding to yellow by the semiconductor laser 44 to form a yellow electrostatic latent image.
Yellow developer 2 in the developing state with +600v applied to 2
6 and a magenta developer 27, a cyan developer 28, and a black developer 38 in a non-developing state to form a yellow toner image. At this time, since a voltage of +800 cm was applied to the collection roller 41 by the high voltage power supply 42, the black toner on the photoreceptor did not fly back from the photoreceptor 40 to the collection roller 41. Without removing static electricity, the corona charger 43 (Scorotron charger, corona voltage: +7kV, grid voltage: 800
The photoreceptor 40 was charged to +810V by V). At this time, the charged potential of the photoreceptor 40 to which the black and yellow toners were attached was 810V. Thereafter, the semiconductor laser 44 is used to expose the signal light corresponding to magenta to form a magenta electrostatic latent image.Then, the photoreceptor 40 is developed using the yellow developer 26 in a non-developing state, and +5oov is applied to the developing roller 33. A magenta toner image was formed by passing through a magenta developing device 27. Thereafter, the photoreceptor 40 was passed through a cyan developer 34 and a black developer 38 in a non-developing state. At this time, the collection roller 41 is powered at +800V by the high voltage power supply 42.
Since the voltage of 100 mL was applied, the black and yellow toners on the photoconductor 40 did not fly back from the photoconductor to the collection roller 41. Next, the photoreceptor 40 is charged again by the corona charger 43 without photostatically eliminating the photoreceptor 40.
was charged to +840V. At this time, the charged potential of the photoreceptor 40 to which only the black, yellow, and magentan toners were attached was 800 square meters. Further, the charged potential of the photoreceptor 40 at the portion where the yellow and magenta toners overlapped became 780V. Thereafter, a semiconductor laser 44 was used to expose signal light corresponding to cyan to form a cyan electrostatic latent image. next,
The photoreceptor 40 is passed through a yellow developer 26 in a non-developing state, a magenta developer 27 in a non-developing state, and a cyan developer 28 in a developing state in which +800V is applied to the developing roller 34 to form a cyan toner image on the photoreceptor 40. Completed color image.

At this time, the collection roller 41 is powered by the high voltage power supply 42 at +800.
Since the voltage (2) was applied, the black, yellow, and magenta toners on the photoreceptor 40 did not fly back from the photoreceptor to the collection roller 41.

The color toner image thus obtained on the photoreceptor 40 was transferred onto paper 47 by a transfer charger 46, and then thermally fixed by a fixing device 48. On the other hand, after the transfer, the surface of the photoreceptor 40 is
Pre-cleaning charger 49 (corona voltage +5.5kV)
After being positively charged, a conductive fur brush 50 to which a voltage of -150 V was applied was pressed against the photoreceptor 40 for cleaning.

As a result, the density of black, yellow, magenta, and cyan is 1.
2, a clear color image with a color density of 1.5 or more of the composite color of red, green, and blue solid areas was obtained.

Here, in order to demonstrate the effects of this example, a comparative example will be shown below. Using the same device as in the above embodiment, this time the collection roller 51 is grounded, and 1+ml1llt is collected from the photoreceptor 40.
and fixed it.

The photoconductor 40 is charged to a charging potential of +900V by a charger 43 (scorotron charger, corona voltage: +7 kV, grid voltage: 1 kV). Then, the semiconductor laser 44 is caused to emit light, and a negative black signal is produced on the photoconductor 40. was exposed to light to form an electrostatic latent image. The latent image is applied to the developing roller 39 by +600
A black toner image was formed by reversal development using a black developing device 38 in a developing state to which V was applied. Thereafter, the photoreceptor 40 was neutralized using a static elimination lamp 45.

Next, the photoreceptor 40 was charged to +600V again using the corona charger 43 (Scorotron charger, corona voltage: +7 kV, grid voltage: 600V).

At this time, the charged potential of the photoreceptor 40 to which the black toner was attached was 600V. Thereafter, the photoreceptor 40 was exposed to signal light corresponding to yellow by the semiconductor laser 44 to form a yellow electrostatic latent image. Next, this photoreceptor 40 is passed through a yellow developing device 26 in a developing state in which +600V is applied to the developing roller 32, a magenta developing device 27 in a non-developing state, a cyan developing device 28, and a black developing device 38 to form yellow toner. formed an image. At this time, since the collection roller 41 was grounded, the black toner from the photoreceptor 40 would fly back to the collection roller 41, resulting in a decrease in black density. Vessel 4
3 (Scorotron charger, corona voltage: +7 kV, grid voltage: 800 V) to charge the photoreceptor 40 at +810 V.
It was charged with electricity. Thereafter, a semiconductor laser 44 was used to expose signal light corresponding to magenta to form a magenta electrostatic latent image.

Next, the photoreceptor 40 was passed through a yellow developing device 26 in a non-developing state and a magenta developing device 27 in a developing state in which +5 oov was applied to the developing roller 33 to form a magenta toner image. Thereafter, the photoreceptor 40 is transferred to the cyan developer 3 in a non-developing state.
4 and a black developing device 38. At this time, since the collection roller 41 is grounded, the black and yellow toners from the photoreceptor 40 are about to fly back to the collection roller 41, and the density of black and yellow is reduced.Next, the photoreceptor 40 is photostatically neutralized. The photoreceptor 40 was again charged to +840V by the corona charger 43 without any trouble. Thereafter, a semiconductor laser 44 is used to expose signal light corresponding to cyan to form a cyan electrostatic latent image. ni＋
The toner was passed through a cyan developing device 28 in a developing state to which 800 V was applied to form a cyan toner image, thereby completing a color image on the photoreceptor. At this time, since the collection roller 41 touched the ground, the black, yellow, and magenta toners would fly back to the collection roller 41 from the photoreceptor 40, and the densities of black, yellow, and magenta would decrease.

The color toner image thus obtained on the photoreceptor 40 was transferred onto paper 47 by a transfer charger 46, and then thermally fixed by a fixing device 48.

As a result, only low-density color images with black, yellow, and magenta densities of 0.6 were obtained.

FIG. 6 is a side view showing a collection roller of a color electrophotographic apparatus according to another embodiment of the invention of the present application. The configuration of this embodiment is the same as that in FIG. 1 except for the collection roller. Here, the same device as in the first embodiment 1 is used, and this time the sixth embodiment
As shown in the figure, a detachment mechanism (driving solenoid) 51 is attached to the collection roller 41 instead of the power source 42, and the collection roller 41 is
1 was grounded.

The photoreceptor 40 is charged to a charging potential of +900■ by a charger 43 (scorotron charger, corona voltage: +7 kV, grid voltage: 1 kV), and then the semiconductor laser 44
was caused to emit light, and a negative black signal was exposed on the photoreceptor 40 to form an electrostatic latent image. The latent image is transferred to the developing roller 39 by +60
A black toner image was formed by reversal development using a black developing device 38 in a developing state to which 0 V was applied. After that, the drive solenoid 5
1 to bring the collection roller 41 close to the photoreceptor (Im)
, the carrier attached to the photoreceptor 40 was adsorbed. after that,
Do not eliminate static electricity from the photoreceptor 40 using the static elimination lamp 45.

Next, the photoreceptor 40 was charged to +600V again using the corona charger 43 (Scorotron charger, corona voltage: +7 kV, grid voltage: 600V).

At this time, the charged potential of the photoreceptor 40 to which the black toner was attached was 600 .mu.m. Thereafter, the photoconductor 40 is exposed to signal light corresponding to yellow by the semiconductor laser 44 to form a yellow electrostatic latent image.The photoconductor 40 is then placed in a developed state by applying +600cm to the developing roller 32. A yellow toner image was formed by passing through a yellow developer 26, a magenta developer 27 in a non-developing state, a cyan developer 28, and a black developer 38. At this time, since the collection roller 41 was separated from the photoreceptor by two distances by the driving solenoid 51, the black toner on the photoreceptor 40 did not fly back from the photoreceptor to the collection roller 41. Next, this time this photoreceptor 4
The corona charger 43 is turned on again without removing the charge from 0.
The photoreceptor 40 was charged to +810 .ANG. (Scorotron charger, corona voltage: +7 kV, grid voltage = 800 .ANG.). Thereafter, a semiconductor laser 44 was used to expose signal light corresponding to magenta to form a magenta electrostatic latent image. Next, the photoreceptor 40 is transferred to the yellow developer 26 in a non-developing state.
A magenta toner image was formed by passing through the magenta developing device 27 in a developing state in which +5 oov was applied to the developing roller 33. Thereafter, the photoreceptor 40 was passed through a cyan developer 34 and a black developer 38 in a non-developing state. At this time, the collection roller 41 is moved 2M from the photoreceptor by the driving solenoid 51.
As a result, the black and yellow toners on the photoconductor 40 did not fly back from the photoconductor 40 to the collection roller 41.Next, the photoconductor 40 was charged again by the corona charger 43 without being photostatically neutralized. The photoreceptor 40 was charged to +840V. Thereafter, a semiconductor laser 44 is used to expose signal light corresponding to cyan to form a cyan electrostatic latent image. A cyan toner image was formed by passing through the cyan developing device 28 in a developing state to which +800V was applied, and a color image was completed on the photoreceptor 40. At this time, the collection roller 41 is moved to -drive solenoid 5.
Since the toner was separated from the photoreceptor by 1 and 2, the black, yellow, and magenta toners on the photoreceptor 40 did not fly back from the photoreceptor 40 to the collection roller 51.

The color toner image thus obtained on the photoreceptor 40 was transferred onto paper 47 by a transfer charger 46, and then thermally fixed by a fixing device 48.

As a result, the density of black, yellow, magenta, and cyan is 1.
2t', the color density of the composite color of red, green, and blue solid areas is 1.5
A clear color image was obtained.

In addition, the above two inventions are based on monochromatic colors such as red, green, and blue, and black.
Not only color electrophotographic equipment that synthesizes colors, but also yellow and
It can also be applied to full-color electronic harp instruments that overlap magenta and cyan toner images. Further, the magnetic collection roller used in the present invention may be any conductive magnet.

As described in detail, according to the present invention, a mechanism for applying a voltage having the same polarity as the charged polarity of the photoreceptor to the collection roller or a mechanism for separating the collection roller from the photoreceptor is provided. By providing this, it is possible to prevent the toner image from flying back from the photoreceptor to the collection roller that removes the carrier attached to the photoreceptor, and to obtain a color electrophotographic device that can obtain a clear and high-density color image. Its practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a sectional side view of a color electrophotographic apparatus according to an embodiment of the present invention, FIGS. 2 and 3 are sectional side views of a conventional color electrophotographic apparatus, and FIG. 4 shows a photoreceptor with toner attached. Fig. 5 is a side view showing the state of corona charging, and Fig. 5 is a side view showing the backlash of toner that occurs when the grounded collection roller approaches the photoreceptor in the state shown in Fig. 4. Fig. 6 FIG. 2 is a side view of a main part of a color electrophotographic apparatus according to another embodiment of the invention of the present application. 26... Developer (yellow), 27... Developer (magenta), 28... Developer (cyan), 38... Developer (black), 40... Photoreceptor, 41...・Recovery roller,
42... High voltage power supply, 43... Corona charger, 44...
... Semiconductor laser, 51... Drive solenoid. Name of agent: Patent attorney Toshio Nakao Haka 1 Meika 2 Diagram

Claims (2)

[Claims] (1) a color image forming means for forming a color image on a photoreceptor by repeating charging, exposure, and development steps for each of a plurality of colors; and a transfer means for transferring the color image on the photoreceptor onto paper; A color electrophotographic apparatus comprising: a collection roller that adsorbs and removes magnetic carriers attached to a photoreceptor by a magnetic brush development method; and a power source that applies a voltage having the same polarity as the charged polarity of the photoreceptor to the collection roller. (2) a color image forming means for forming a color image on a photoreceptor by repeating charging, exposure, and development steps for each of a plurality of colors; and a transfer means for transferring the color image on the photoreceptor onto paper; A color electrophotographic apparatus comprising: a collection roller that adsorbs and removes magnetic carriers attached to a photoreceptor using a magnetic brush development method; and a mechanism that moves the collection roller toward and away from the photoreceptor.